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A magnitude-8 earthquake has struck in the northern Pacific but is not linked to this morning's 7.2 quake closer to New Zealand, GeoNet says.

The North Pacific quake was off the coast of the Rat Islands, about 2000 kilometres west of the Alaskan peninsula at 8.53am (NZ time).

It was initially recorded as a magnitude 7.2 quake but this was revised to magnitude 8 a short time later. It was at a depth of 114km. A tsunami warning was issued for coastal areas of Alaska.

It followed a 7.2 earthquake south of Raoul Island at 7.19am, which DOC staff on the island described as a "rocking good time".

That quake was initially reported to be 5km deep, but was revised to 30km.

Raoul Island is part of the Kermadec Island group, about 1100km northeast of New Zealand.

GeoNet duty seismologist Caroline Holden said the timing of the quakes was interesting but there was nothing to relate them other than both occurred in the Ring of Fire.

The Ring of Fire is a 40,000km horseshoe-shaped area of the Pacific Ocean, where a large number of earthquakes and volcanic eruptions occur.

Of the Raoul Island quake, Holden said it was too small to trigger a significant tsunami, though the situation was being monitored.

Civil Defence said there was no tsunami threat to New Zealand.

The quake also caused two "ghost quake" readings for New Zealand's North Island, Holden said.

The "ghost" quakes - recorded near Palmerston North and on the East Cape - were monitors being tricked by the more-distant Kermadec shake.

According to GeoNet's initial reports, one magnitude-5 quake was centred near Feilding, north of Palmerston North, at 7.21am. It was described as a "moderate" quake. Also at 7.21am, Geonet gave a false reading of a "severe" 5.2 quake near Te Araroa on the East Cape.

However GeoNet later tweeted "A 7.2 quake in the Kermadecs has upset our system this morning! Two large 'ghost quakes' posted in the North Island are not real."

At 9.10am, a 4.4 magnitude quake was recorded 35km northeast of Te Araroa in the East Cape.

It was at a depth of 90km, GeoNet said.

Department of Conservation Raoul Island ranger Paul Rennie said DOC had four staff and two volunteers on Raoul island but they were all accounted for and unharmed.

"They described it as a rocking good time," he said.

"In terms of where they are at the moment, there are no reports of damage but they will be going out and assessing if there is any this morning."